The present invention generally relates to a semiconductor electronic device structure comprising at least one porous SiCOH (pSiCOH, carbon-doped oxide) layer having improved interfacial strength (adhesive and cohesive strength near the interface) to a dielectric or conducting layer. The improved interfacial strength is caused by the presence of transition layers that are formed between the porous SiCOH layer and the dielectric or conducting layer. The transition layers are formed in the present invention by starting the deposition of a specific layer, while a surface preparation plasma is still present and active in the reactor.
The continuous shrinking in dimensions of electronic devices utilized in ULSI circuits in recent years has resulted in increasing the resistance of the BEOL metallization without concomitantly decreasing the interconnect capacitances. Often interconnects are even scaled to higher aspect ratios to mitigate the resistance increases, leading to increased capacitances. This combined effect increases signal delays in ULSI electronic devices. In order to improve the switching performance of future ULSI circuits, low dielectric constant (k) insulators and particularly those with k significantly lower than silicon oxide are being introduced to reduce the capacitance.
The low-k materials that have been considered for applications in ULSI devices include polymers containing Si, C and O, such as methylsiloxane, methylsilsesquioxanes, and other organic and inorganic polymers which are fabricated by spin-on techniques or, Si, C, O and H containing materials (SiCOH, SiOCH, carbon-doped oxides (CDO), silicon-oxycarbides, organosilicate glasses (OSG)) deposited by plasma enhanced chemical vapor deposition (PECVD) techniques. In an effort to decrease the dielectric constant further, Grill et al. U.S. Pat. No. 6,312,793, the disclosure of which is incorporated by reference herein, discloses porous low-k dielectrics such as porous SiCOH. The incorporation of the low-k dielectrics in the interconnect structures of integrated circuits (IC) often requires the use of other dielectric materials as diffusion barrier caps or etch-stop and chemo-mechanical polishing (CMP) hardmasks. The adhesion among the different layers in the complex structures of an IC device is often too low, resulting in delaminations during the processing of the device, dicing into chips, or reduced reliability in response to mechanical stresses imposed by typical chip packaging materials. Often even when the adhesion is adequate, the deposited low-k film may possess degraded cohesive strength near the initial interface that is formed during deposition, and adhesion testing leads to fracture within this initial layer, which may be from single to tens of nm thick. Without careful failure analysis, the low failure energies from adhesion testing of such cases may be mistakenly attributed to poor interfacial adhesion, rather than substandard cohesive strength of the near-interface low-k film. This is especially true for interfacial strength (adhesive and cohesive strength near the interface) of a carbon doped oxide dielectric comprised of Si, C, O and H (SiCOH) to other hardmask or diffusion barrier cap dialectics, such as SiN, SiC(H) or SiCN(H).
It would thus be highly desirable to provide a semiconductor device comprising an insulating structure including a multitude of dielectric and conductive layers with good interfacial strength among the different layers, and a method for manufacturing such semiconductor devices.
Various solutions have been proposed for increasing the interfacial strength of low-k dielectrics to the previous layer.
Conti et al. U.S. Pat. Nos. 6,570,256 and 6,740,539, the disclosures of which are incorporated by reference herein, disclose a carbon-graded layer which can be employed within the initial region of a carbon-containing organosilicate layer to improve adhesion to the underlying substrate. However, the so-called carbon-graded layer consists of successive distinct layers with the concentration of carbon increasing in steps from layer to layer. Thus, each carbon-graded layer is in actuality a layer of constant carbon concentration.
Edelstein et al. U.S. Pat. No. 7,067,437, the disclosure of which is incorporated by reference herein, discloses a carbon-graded transition layer between the underlying dielectric or conducting layer and the dense SiCOH layer. The carbon-graded transition layer may be oxygen rich and/or carbon depleted.
The foregoing references developed structures containing dense dielectric layers. The present inventors have found that porous dielectric layers present certain difficulties in their formation, particularly due to the carbon generated by the porogen used to form the pores in the dielectric. Another difficulty arises when the precursors used to form porous dielectric layers react rapidly in the gas phase, forming particulates which settle on the manufacturing substrate, an occurrence known as gas phase nucleation (GPN). Particles then cause patterning defects and other manufacturing failures. The present inventors have analyzed those methods (conditions) that produce GPN and the preferred methods (conditions) that do not produce GPN.
Accordingly, it is a purpose of the present invention to provide a semiconductor device structure and method for manufacturing an insulating structure comprising a multitude of dielectric and conductive layers with improved interfacial strengths between at least one porous SiCOH layer and other layers in the interconnect structure.
It is another purpose of the present invention to achieve these improved interfacial strengths by a process which would allow continuous grading of the interfaces.
Further purposes and advantages of the present invention will become apparent after referring to the following description of the invention considered in conjunction with the accompanying drawings.